1. Field of the Invention
This invention relates to a data recording apparatus and more particularly to a data recording apparatus having a function of verifying recorded data.
2. Description of the Related Art
There are digital data recorders of two known kinds, one using a disc-shaped recording medium such as a floppy disc and the other a tape-shaped recording medium.
In the data recorders of these kinds, a dropout in recorded data causes a serious defect. In recording data, therefore, the recorded data must be verified in order to assure the reliability of the record. The conventional data recorder is arranged to make such verification in a manner suited for a recording method, the recording medium used and other conditions.
FIG. 1 of accompanying drawings shows recording tracks formed on a recording medium by a typical conventional data recorder of the kind using a disc-shaped recording medium. FIGS. 2(a) to 2(c) show the allocation of data on the recording tracks of FIG. 1. A reference numeral 1 denotes the disc-shaped recording medium; and 2a, 2b, 2c and 2d denote recording tracks obtained in different sectors. In the data recorder of this kind, data is recorded in a plurality of sectors as shown in FIG. 2(b) in accordance with an index pulse which is as shown in FIG. 2(a). In FIG. 2(b), a reference symbol GAP denotes a part in which no data is recorded. Data is allocated within each of the sectors 0, 1, 2, 3, etc. as shown in FIG. 2(c). In FIG. 2(c), a symbol DATA denotes main data to be recorded; a symbol DATA Sync denotes data provided for the purpose of synchronizing the main data; a symbol ID denotes sub-data such as control data or the like; a symbol ID Sync denotes data provided for synchronizing the sub-data; and a symbol CRCC denotes a known cyclic code (hereinafter referred to as CRCC). The data recorder of this kind verifies recorded data as follows: Reproduction is performed immediately after recording. A data error occurring state is monitored with the CRCC which is reproduced. In cases where data errors are found to be occurring to an excessive degree, the same data is again recorded in the same phasic part of the recording medium.
Referring to FIG. 3, in the case of the data recorder of the kind using a tape-shaped recording medium, a verifying head 6 is disposed on the downstream side of a recording head 5 in the direction of arrow 4 in which the tape 3 is to be transported. The error occurring state of data recorded by the recording head 5 is monitored by means of a CRCC or a parity check code reproduced by the verifying head 6. If the data error is found to be excessively occurring, data recording is suspended by bringing the transport of the tape 3 to a stop.
In the case of the data recorder using the disc-shaped recording medium, however, the amount of data recordable on the medium is limited. The recorder of this kind is, therefore, not suitable for recording data in a great amount. Meanwhile, the data recorder using the tape-shaped recording medium inevitably has a reduction in average data transmitting bit rate, because the recording is suspended on every occasion of a data error during recording, although the data is recordable in a large amount. The recorder, therefore, requires an excessively long period of time for recording.
In the case of such data as image data that can be adequately reproduced through data interpolation, etc. without completely restoring all the recorded data, much time is wasted by the above stated suspension of recording. Besides, if the head which performs reproduction during the process of verification comes to trace a part other than an applicable recording track, a noise component would mix in the data to be mistaken for a data error even when recording is adequately performed. This tendency increases accordingly as the track width decreases.
Furthermore, during the process of reproduction, the tape is temporarily rewound to reproduce data from the same track every time a data error incapable of correction occurs. This causes an excessively long period of time also for reproduction. The long period of time required for recording and reproduction greatly degrades the utility of the data recorder. Hence, this drawback has prevented the data recorder of the kind using the tape-shaped recording medium from becoming popular.